A fuel pump utilizes oil or other like fluid (herein referred to as “lubrication fluid”) for the lubrication of moving components enclosed within the pump housing. In traditional fuel pumps with oil lubricated lower ends, such as those utilized in common rail fuel systems, oil is provided to the fuel pump by a pressurized feed and is drained out the driven end of the pump housing. Often, this end of the housing mates with either the front or rear housing of the engine. Thus, oil drained out of the fuel pump is returned to the engine pan.
Each pump typically has a driven gear mounted on a central camshaft that extends out of the pump housing. The camshaft is usually mounted in a bearing journal. The driven gear is driven by a mating drive gear connected either directly, or indirectly, to the engine drive train/crankshaft. To allow for oil drainage out of the fuel pump, holes are drilled in the pump housing. The placement of the holes must be outside of the bearing journal diameter for the camshaft. Typically, the holes are drilled to the right, to the left, or below the camshaft. Various size and positional constraints may cause the holes to be positioned adjacent to the meshing of the teeth of the driven gear and the mating drive gear.
The height of the drain holes in the pump housing determines the amount of oil or lubrication fluid that remains in the pump housing after the engine has shut down (“sump level”). Some level of lubrication fluid in the pump housing is desired for the cooling of components during start-up of the pump. Due to economies of scale, the same pump may be utilized on different engines. The positioning of the fuel pump on each of these different engines may vary. For example, while on some engines the fuel pump may be mounted in a vertical position, on other engines the fuel pump may need to be mounted such that the fuel pump is rotated clockwise or counterclockwise from the vertical position. Such situations may result in a drain hole being positioned below the desired sump level. As a consequence, a lower than desired sump level of lubrication fluid in the pump housing will occur. The lower position of the drain hole also increases the possibility that any debris that may have sunk to the lower portion of the pump housing will flow out of the lower drain hole and into the meshing of the teeth of the drive and driven gears.
U.S. Pat. No. 6,112,726 (“Saito et al.”) issued Sep. 5, 2000 is an example of prior art related to fuel pumps. FIGS. 7-8 of Saito et al. disclose a fuel pump 111 encased in a housing 155. The lower wall of this housing 155 has a drain passage 158 that drains lubricant back to an oil reservoir 160. Disadvantageously, the drain position of Saito et al. increases the likelihood that debris within the housing may block the drain. A better design is needed.